Add call to /institution_selected endpoint

[tillh-stripe]

Summary

This pull request adds support for calling the /institution_selected endpoint in the institution picker, which will be used by #10397.

(cc @mats-stripe)

Motivation

Testing

• Added tests
• Modified tests
• Manually verified

Screenshots

Before	After
before screenshot	after screenshot

Changelog

[github-actions]

Diffuse output:

OLD: identity-example-release-base.apk (signature: V1, V2)
NEW: identity-example-release-pr.apk (signature: V1, V2)

          │          compressed           │         uncompressed         
          ├───────────┬───────────┬───────┼───────────┬───────────┬──────
 APK      │ old       │ new       │ diff  │ old       │ new       │ diff 
──────────┼───────────┼───────────┼───────┼───────────┼───────────┼──────
      dex │     2 MiB │     2 MiB │   0 B │   4.1 MiB │   4.1 MiB │  0 B 
     arsc │     1 MiB │     1 MiB │   0 B │     1 MiB │     1 MiB │  0 B 
 manifest │   2.3 KiB │   2.3 KiB │   0 B │     8 KiB │     8 KiB │  0 B 
      res │ 302.9 KiB │ 302.9 KiB │   0 B │   457 KiB │   457 KiB │  0 B 
   native │   6.2 MiB │   6.2 MiB │   0 B │  15.8 MiB │  15.8 MiB │  0 B 
    asset │   7.4 KiB │   7.4 KiB │   0 B │   7.1 KiB │   7.1 KiB │  0 B 
    other │  95.2 KiB │  95.1 KiB │ -12 B │ 182.4 KiB │ 182.4 KiB │  0 B 
──────────┼───────────┼───────────┼───────┼───────────┼───────────┼──────
    total │   9.6 MiB │   9.6 MiB │ -12 B │  21.6 MiB │  21.6 MiB │  0 B 

 DEX     │ old   │ new   │ diff      
─────────┼───────┼───────┼───────────
   files │     1 │     1 │ 0         
 strings │ 20144 │ 20144 │ 0 (+0 -0) 
   types │  6235 │  6235 │ 0 (+0 -0) 
 classes │  5026 │  5026 │ 0 (+0 -0) 
 methods │ 30045 │ 30045 │ 0 (+0 -0) 
  fields │ 17388 │ 17388 │ 0 (+0 -0) 

 ARSC    │ old  │ new  │ diff 
─────────┼──────┼──────┼──────
 configs │  164 │  164 │  0   
 entries │ 3644 │ 3644 │  0

APK

    compressed    │   uncompressed   │                                           
──────────┬───────┼───────────┬──────┤                                           
 size     │ diff  │ size      │ diff │ path                                      
──────────┼───────┼───────────┼──────┼───────────────────────────────────────────
 25.7 KiB │  -6 B │    64 KiB │  0 B │ ∆ META-INF/MANIFEST.MF                    
   29 KiB │  -4 B │    64 KiB │  0 B │ ∆ META-INF/CERT.SF                        
    271 B │  -1 B │     120 B │  0 B │ ∆ META-INF/version-control-info.textproto 
  1.2 KiB │  -1 B │   1.2 KiB │  0 B │ ∆ META-INF/CERT.RSA                       
──────────┼───────┼───────────┼──────┼───────────────────────────────────────────
 56.1 KiB │ -12 B │ 129.4 KiB │  0 B │ (total)